EdgeFEM3DwPrec ver. 2017,
Release March 2018. Release March 2018. The program provides
frequency-domain finite-element modeling of electric field
responses in 3D anisotropic conductive medium. The program user
interface is the same as EdgeFEM3D (Cai and Zhdanov, 2016). The
crucial difference between the two programs is that EdgeFEM3DwPrec
is leveraged with Green’s Function (GF) and contraction operator
(CO) preconditioners (Yavich and Zhdanov, 2016), while EdgeFEM3D
uses simple Jacobi preconditioner. Consequently, EdgeFEM3DwPrec
provides much faster modeling than EdgeFEM3D. The medium is
assumed to be formed by a layered background and finite number of
rectangular inclusions. The secondary field approach (Zhdanov,
2017) is implemented; thus sources are incorporated via the
background field. The latter is computed with the green3d module.
The finite-element grid is assumed to be rectangular and
nonuniform. We appreciate that more general hexahedral grids might
be more attractive for modeling of complex geological structures;
we thus plan to extend this code respectively in the future..
Authors: Nikolay Yavich, Hongzhu Cai, and Michael S. Zhdanov.
References:
Cai, H., and M. S. Zhdanov, 2016, EdgeFEM3D
user manual.
Yavich, N., and M. S. Zhdanov, 2016,
Contraction pre-conditioner in finitedifference electromagnetic
modelling, Geophysical Journal International, 206, 1718 - 1729.
Zhdanov, M. S., 2017, Foundations of
geophysical electromagnetic theory and methods: Elsevier.

GREEN3D,
release March 2010. The MatLab shell of the Fortran 77 library
GREENLIB for computing the normal fields and volume integrals of
electromagnetic Green's tensors. This program is designed to help
the development of electromagnetic modeling and inversion
programs. It is an easy-to-use MATLAB function which can be called
up anywhere in the MATLAB environment. Using this library, the
software developer is freed from coding the excessively complex
algorithms for Green's tensors and different electromagnetic
fields in a layered medium.
Author: Gabor Hursan
References:
Xiong, Z., 1992, EM modeling of three-dimensional structures by
the method of system iteration using integral equations,
Geophysics, 57, 1556-1561.
Zhdanov, M. S., and G. V. Keller, 1994, The geoelectrical methods
in geophysical exploration: Elsevier, 873 pp.
G. Hursan, 1999, A Fortran 77 Library for Computing the Normal
Fields and Volume Integrals of Electromagnetic Green's Tensors:
Proceedings of the CEMI 1999 Annual Meeting.

TSEMRSA ver. 2017,
Release March 2018. Subsurface targets, hydrocarbon reservoirs or
ores and mineral deposits for example, are usually characterized
by different electric conductivities with the bedrocks or
sediments. An induced anomalous electromagnetic field will be
generated by the targets when they are excited by an external
electromagnetic field. The anomalous field manifests itself as a
fast and good indication of the location and range of the
subsurface targets. However, the anomalous field is usually weak
and unrecognizable due to strong background field and
environmental noise. The TSEMRSA software package is specially
designed to enhance the response from the targets and provide a
fast imaging tool to locate subsurface targets laterally. The
concept of synthetic aperture is employed in this package to
uplift the signal from the targets. The current 2017 version of
the TSEMRSA software package is specially designed for the survey
configuration of marine towed streamer electromagnetic method, but
with the prospect of supporting airborne electromagnetic survey in
future versions.

MultiGrav3D ver. 2017,
Release March 2018. The MultiGrav3D is a PGI CUDA Fortran based
software package for 3D multinary inversion of gravity and/or full
tensor gradiometry (FTG) data. The code uses the multinary
transformation of the model parameters to explicitly exploit the
sharp contrasts of the density between the host media and
anomalous targets in the inversion of gravity data. The multinary
transformation is based on the given values of density and error
functions. We also provide the option of an adaptive technique for
selecting the corresponding standard deviations specifically
designed for the multinary inversion of the field data. The code
can also be run as a traditional inversion tool using minimum norm
support by setting the standard deviation as some large value, for
example, 0.5. The code is written in CUDA Fortran, which requires
Nvidia graphics cards and CUDA toolkit installed. The code must be
run with the PGI Fortran compiler.

MT3D ver. 2017,
Release March 2018. The MT3D software package performs 3D
inversion of magnetotelluric (MT) data. FullMT impedance tensor
(Zxx, Zxy, Zyx, and Zyy) with the option of adding a magnetic
tipper (Wzx and Wzy) can be inverted over inhomogeneous geological
formations for 3D conductivity distribution and distortion matrix.
This problem is associated with computing the 3D electromagnetic
(EM) fields and Fréchet derivative used in minimization. We use a
rigorous integral equation (IE) method for forward modeling
(Zhdanov, 2002), and quasi-Born approximation for Fréchet
derivative calculation (Gribenko and Zhdanov, 2007). MT data
inversion is an ill-posed problem. To obtain a stable solution we
apply the Tikhonov regularization method (Zhdanov, 2002, 2015).
The inversion is based on the Gauss-Newton method in data space
(Gribenko and Zhdanov, 2017).

JOINT3D ver. 2016,
Release March 2017. The JOINT3D is a MATLAB software package for
3D joint inversion of potential field and airborne electromagnetic
(EM) data using Gramian constraints (Zhdanov et al., 2012). The
packages is capable for either direct or structural correlation
between two physical properties, e.g., density and log of
conductivity, magnetic susceptibility, and log of conductivity. In
the potential field forward modeling, we discretize the modeling
domain into a set of rectangular prisms and evaluate the volume
integral in each prism using single-point Gaussian integration.
The airborne EM forward modeling and Fréchet computation are based
on the integral equation method (Hohmann, 1975) and quasi-born
approximation (Gribenko and Zhdanov, 2007), respectively. The
package is compatible with both minimum norm and maximum smooth
stabilizers. We solve the joint inversion problem using the
regularized conjugate gradient method (Zhdanov, 2002). Please
refer to the JOINT3D manual and examples for running the
algorithm.

GRAVMTBASE ver. 2016,
Release March 2017. The GRAVMTBASE is a MATLAB joint inversion
software package for depth to basement estimation using gravity
and electromagnetic (e.g., MT) data (Cai and Zhdanov, 2015a,
2015b; Cai and Zhdanov, 2016). The software using Cauchy-type
integral transform and integral equation methods for the modeling
of gravity and MT data, respectively. The algorithm discretizes
the interface between the sediments and basement rocks. In the
inversion, the depth to basement and the physical property
contrast (e.g., density contrast, conductivity values) between
sediment and basement will be recovered simultaneously. The joint
inversion can reduce the uncertainty comparing to the separate
inversion of either gravity or MT data.
Please refer to the GRAVMTBASE manual and examples for running the
algorithm.

JOINT3D ver. 2015,Released
March 2016. The JOINT3D software package performs 3D joint
inversion of gravity and magnetic data. It works for any
combination of the gravity (Gx, Gy, Gz, Gxx, Gyy, Gzz, Gxy, Gzx,
Gzy, Gd) and magnetic components (TMI, Hx, Hy, Hz). The joint
inversion code uses the Gramian constraints (Zhdanov et al., 2012)
to enhance either direct or structural correlations between two
physical properties, which are the density and magnetic
susceptibility or the density and magnetization vector, depending
on the existence or not of remanent magnetization. We discretize
the modeling domain into a set of rectangular prisms and evaluate
the volume integral in each prism using single-point Gaussian
integration in the forward modeling and Fréchet computation. The
code is compatible with both minimum norm and maximum smooth
stabilizers. We solve the joint inversion problem using the
regularized conjugate gradient method (Zhdanov, 2002).

PF3D ver. 2011,
Release March 2012. The PF3D ver. 2011 is a MATLAB software
package for 3D modeling and inversion of potential field data
which includes magnetic field, magnetic gradient tensor
components, gravity field, and gravity gradient tensor components.
The code is designed for 3D inversion of the data collected on a
variable surface, including the option for joint inversion of the
different gravity or magnetic field and tensor field components.
For inversion, the code uses the approach known as the re-weighted
regularized conjugant gradient method, or RRCG method, with
focusing stabilizers to produce compact geophysical images. It
also utilizes a technique to naturally impose model constraints by
computing iterations in the space of logarithmic model parameters.
Authors: Martin Cuma and Michael S. Zhdanov
References:
Portniaguine, O., and M. S. Zhdanov, 1999,
Focusing geophysical inversion images: Geophysics, 64, 874-887.
Zhdanov, M. S., 2002, Geophysical inverse
theory and regularization problems: Elsevier.

GG3Dmigration ver. 2013,
Release March 2014.The GG3Dmigration ver. 2014 is a MATLAB
software package for migration of the gravity and/or gravity
gradiometry data in order to image a 3D density distribution. The
gravity and/or gravity gradiometry data can be collected on a
variable surface. The major novel feature of the code is the
ability to select an arbitrary combination of gravity field and
gravity tensor components and migrate them jointly. The migration
can be done on a large scale and within an arbitrary selected
domain. The software package includes the source code, user manual
and examples. Also, it includes a code to produce the
cross-section image for a convenience. The software is easy to
maintain and to use.
Authors: Le Wan and Michael S. Zhdanov
References:
Zhdanov, M. S., X. Liu, G. A. Wilson, and L.
Wan, 2011, Potential field migration for rapid imaging of gravity
gradiometry data: Geophysical Prospecting, 59, 1052--1071.

CauchyGrav3D ver. 2014,
Release March 2015. The CauchyGrav3D ver. 2014 is a MATLAB
software package for 3D modeling and inversion of gravity data
caused by a density contrast interface model. The code uses a
novel approach based on 3D analogs of Cauchy type integrals for
the modeling and inversion of gravity and gravity gradiometry data
caused by the density contrast model (Zhdanov, 1988; Cai and
Zhdanov, 2014, 2015). The code can be used in Windows or Linux
machine with MATLAB installed. For this release, the density
contrast is assumed to be a given constant in the inversion. The
code outputs the depth to basement. This package contains two main
programs for forward modeling and inversion. The program
Cauchy3DFWD is the program for forward modeling, while the program
Cauchy3DInv is for inversion.
Authors: Hongzhu Cai and Michael S. Zhdanov
References:
Cai, H., and M. S. Zhdanov, 2014, Modeling and inversion of
magnetic anomalies caused by sediment-basement interface using 3D
Cauchy-type integrals: IEEE Geoscience Remote Sensing and Letters,
12 (3), 477—481.
Cai, H., and M. S. Zhdanov, 2015, Application of Cauchy-type
integrals in developing effective methods for depth-to-basement
inversion of gravity and gravity gradiometry data: Geophysics, 80
(2).
Zhdanov, M. S., 1988, Integral transforms in geophysics:
Springer-Verlag.